Move LightpackMathTest to gtest.
Fix GrabCalculationTest and change it to gtest.
Move SettingsSourceMockupTest to gtest.
Move AppVersionTest to gtest.
Fix GrabCalculationTest and accumulateBufferFormatArgb
Move GrabTests to gtest.
Move SettingsTest to gtest.
Move LightpackCommandLineParserTest to gtest.
Suppress Qt messages in Settings while runnning tests.
Move LightpackApiTest to gtest.
Sort sources lines in tests.pro file.
Move mockups classes to mocks/ dir
Set gtest submodule to track fixed version of gtest.
Fix warning about comparing QtMsgType variable.